PUNTO FIJO, Venezuela – Residents who live near Venezuela's largest oil refinery say they smelled a strong odor of sulfur hours before a gas leak caused an explosion that left at least 39 people dead and more than 80 people injured.

The Amuay refinery was still burning on Sunday more than a day after the blast, sending up a thick column of black smoke.

Residents in a neighborhood next to the refinery said that starting about 7 p.m. on Friday they noticed the unusually strong odor. Government officials say the blast occurred about 1:15 a.m. on Saturday when the gas leak created a cloud that ignited.

The cause of the disaster is under investigation.

Gabriela Nunez, a housewife who lives near the refinery, said she noticed the gas odor on Friday night and then hours later came the shock wave.

"All the windows shattered, the iron doors opened, the wooden doors broke," Nunez said. She returned to her home on Saturday night to gather belongings, saying she was worried about looters who had stolen goods from nearby stores hours after the explosion.

"That forced us to come back, even though we're afraid, to save what can be saved and secure our houses," Nunez said.

A total of 209 homes and 11 businesses were damaged in the explosion, and a National Guard post next to the refinery was destroyed, Vice President Elias Jaua said late Saturday. He said 18 of the victims were National Guard soldiers.

President Hugo Chavez on Saturday declared three days of mourning in the country.

Amuay is among the world's largest refineries and is part of the Paraguana Refinery Complex, which also includes the adjacent Cardon refinery. Together, the refineries process about 900,000 barrels of crude per day and 200,000 barrels of gasoline.

Oil Minister Rafael Ramirez said the country has enough fuel in storage, "10 days of inventories," to keep the Venezuelan market fully supplied with gasoline and diesel.

He said fires were still burning in two fuel storage tanks on Sunday but that other "process areas" of the refinery have been otherwise unaffected. Once the flames are completely extinguished, Ramirez said, "we have the ability to restart our refinery in two days."